Has there ever been any mod that allow the player to adjust transmission gears?

Normally, one can select the number of gears and the differential ratio. Has there been a point where the player could, say, change the maximum speed of first gear?

For example, the old Tiger tank has 8 forward gears. However, the gear ratios are spread so wide that it's like an improvised 15 forward gears. Simulating this within the normal system means you have to sacrifice top speed. To be exact, simulating a 15:1 first gear ratio with a maximum of 5 gears means your top speed goes from the intended 25 mph to 8 mph.